Low frequency mobile glow discharge system



1944. H. c. METTLER 2,354,696

LOW FREQUENCY MOBILE GLOW DISCHARGE SYSTEM Filed Nov. 12, 1940 2 Sheets-Sheet l POWER N PUT CONTROLLER n'urllnlunvnnnnuuuuununnllnnnnuannnnnnnnnlnninnnuulnlnnuuunnunnunnnIn INVENTOR #41. C. Mrrnse BYWM ATTORNE Aug. 1, 1944. H. c. METTLER LOW FREQUENCY MQBILE GLOW DISCHARGE SYSTEM Filed NOV. 12, 1940 2 Sheets-Sheet 2 FIG. 7

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FIG: 11 INVENTOR.

#44 C? fife-r7452 BY QQOw\b\ M HTTORNEY [lllllllll Patented Aug. 1, 1944 Low moumvcrmonnlncmw I DI SC HARGE SYSTEM' 1 Hero. Meanin AngelespCaliL, assignor-of, a one-half to LloydSpencenLosAngeles,Calif; Application November 12, 'iss'oisejr'i No.' 365,206

26; Claims.

My invention relates Ito low frequency mobile glow discharge systems; that is, to glow discharge system's incorporating 1 so-called ffneonf' tubing for theipur'pose of producing a progressive movement of light through a sign or display so asto I give the effect of writing. I I i a I Among the objects oimy invention are; f'

First, tolprovide a mobile glow disch'argesystem ,whichproduces in alen'gth of glow discharge or neon, tubing, when operated by commercial alternating current, such a sixty cycle current,

apmgressive illumination or writing efi'ect, similar to that accomplished by the' use of audio or radio frequency current, such as disclosedin the KayserPatent No. 1,939,903; I Second, to providev a mobile glow discharge system which may be operated through a conventional neon" transformer, controlling or varying the voltage'output from such transformer to effect a progressive movement of light through the fneon,or glow discharge tubing; Third, to provide a mobile glowdischarge system which incorporates substantially conventional glow discharge tubing ,w hether containing "neon or other gases, or mercury; and whether plain or coated withfluorescent material;

Fourth, to providea mobile glow discharge system employing a series of relatively short glow discharge tubes, 'or longer tubes f having intermediate electrodes, the sections being caused to glow in sequence without commutatingor otherwisemaking and breaking high voltage connections between the tubing sections and the high voltage side] of the transformer which supplies power to the tubing, the. progressiveor mobile controlof illumination in the tubing sections being entirely controlled in theprimary of the transformer orother low voltage circuit.

Fifth. to provide a mobile glow discharge system which is particularly easy to install and service,and which is inherently designed to operatewithout attention for longperiods of time under adverse conditions, I,

Sixth, to provide a mob le glow discharge system where n a single glow discharge control unit is inherently capable of controlling a materially reater footage of tubing than. has heretofore been possible with high frequency mobile glow discharge controllers; v V I Seventh, to provide a mobile glow discharge system whichdoes not in any manner increase bombardment of or current load on the electrodes of the glow d scharge tubing beyondthat im osed by a conventional neon transformer; fu thermore the excessive current loadginherent in high frequency mobile glow dischargesystems, particularly on the input electrode at which the progressive animation starts is entirely eliminated; and, 7 i- I Eighth, to provide amobile glow, discharge sys- (Cl; 315+1s7) 'temWherebyjnot "onlylalwriting or pro ressive illumination eflectmay be obtained, but 'all manner ofmobile eifects may be obtained,al1 without necessitating, changelin the transformer or its voltagecontrol means, thus providinga mobile glow discharge system which is particularly fle i I ,With the above andother objects in view as may appear hereinaftenreferenee is dlrected to the accompanyingjdrawingsin which:

Figure 1 is a wiring diagram illustrating one form of my low frequency mobile glow discharge system;

Figure 2 is a wiring diagram illustratinganother form thereof; 1 A Figure 3 is another wiring diagram illustrating a combination of the circuits shown in Figures land 2; 'fi l1 a Figure 4 is a typical cross-sectional view of a neon?v tubing having a metallic coating thereon as employejdlin theexercise-of, my invention to produce a capacity effect;., i v x Figure 5 illustrates afragmentary length lof "neon tubing having a'wrapping of wire thereabout for purposes similar to Figure 6; and v Figure 6 is a fragmentary sectional view of a neon tube illustrating a further modified. construction wherein the resistance network-is disposed within the "neon, tube. i l ,Figure '7 is a wiring diagram, of an arrangement of my invention wherein a moving brush transformer controls a plurality oi' tubing sections simultaneously: q u

Figure 8 is a wiring diagram of a modified form of moving brush transformer which controls a plurality of tubing sections in sequence; 3

j Figure 9is awirlng diagram of another modifled form of moving brush transformer in which the illumination in a plurality of tubing sections is caused to progress and .rec'ede in time displaced relation; l i l i Figure 10 is a wiring diagram of a Thyratron control circuit controlling the. primaryside 01' a neon tubing transformer; and, 45 Figure 11 is a wiring diagram similar to Fig. 10 in which the Thyratron control is located in the sedondary circuit of the neon tubing transforme c 1 g Glo discharge tubing embraces what'is'popularly termed neon" tubing such, as used in signs or displays. lActuallysuchtubing may contain any one of several of the rare'gases, mercury vaoor or mixtures, and'may be, internally coated with fluorescent material. Glow. discharge tubing is caused to ionize by; application of high voltage and, under normalrconditions,-breaks down or ionizes instantly throughout its length without hint of progressive illumination. y p

When radio frequency is applied to such tubing, 60 the glow discharge will not necessarily extend but may be produced with audio frequency. The

charge column within the neon tubing is provided between the first intermediate electrode 4 and the ground electrode 3. Interposed therein and in series with each other are a plurality of resistors 0. Leads ID from the several intermediate electrodes 4 are connected to the path 8 between the resistors.

1 The input electrode 2 is connected to the high controllingfactor is the amount of distributed capacity along the tubing. That is, at radio frequency, there is sumcient capacity between the glow discharge column and the surrounding air to cause sufficient leakage or radiation to ground or the return side of the circuit to produce the desired writing effect. As the frequency is lowered,

the' distributed capacity 'must be increased in order to produce a similar effect. This is accomplished by bringing the tubing into close proximi'ty to a metal backing, by wrapping with wire, or by partially itself. l

y In any event, the leakage along the tubing to: the return side of the circuit causes a gradation in trode to the end of the ionized column'.' IfLthe frequency-capacity relationship is proper the noticeable attenuation is quite short so thatthere is a definite demarcation between the ionized coating with 'inetal'the tubing voltage end of a secondary coil l I of a neon transformer II, the other end thereof being grounded. The primary I! of said neon transformer is connected with a source of power through a suitable power controller I4.

A conventional neon transformer is so constructed that it passes only a-predetermined current when the secondary is shorted. The open circuit potential between the ends of thejsecondary of a neon transformer ranges from 4,000 to 15,000 volts depending upon the length of tubing it is intended to handle. The short-circuit currentis limited, and ranges from 12 to 120 milliamperes depending upon the intensity desired in the neon tubing. Current limitation is accomplished in the brilliancy of illumination from the input elec-v current'frequency, in other words, several hundred cycles cycles.

Applicant has found however, that by providing a resistance network paralleling the glow discharge column, the network being electrically connected at spaced points therewith, and in addition tothe'capacity relation between the glow discharge column andthe return side of the circuit, a very satisfactory progressive or mobile illumination may be effected, at commercial frequencies; More specifically, reference is directed to Figure 1. A length of neon tubing i is provided with input and ground electrodes 2 and '3, respectively, and intermediate electrodes 4. Or, these electrodes may be termed an anode 2, main cathode I, and auxiliary cathodes 4. All are preferably the cold type used in standard neon tubing. The tubing may be a single piece or divided into independent tubing sections connected in series, in the as 'distinguished'fro'm' fifty or sixty standard type of neon transformer by a magnetic shunt in the iron core. It is essential that the current be limited as the neon tube has a comparatively low resistance when ionized and, unless the current is limited the'electrodes will burn up. Thus, essentially, a neon transformer is a high potential, limited current transformer.

The character or manner of progressive or mobile illumination in the neon tubing l is dependent on the values selected for the different resistors. To produce a substantially uniform progression ofillumination from the input electrode 2 to the'ground electrode 3 of the neon tubing, the' resistors decrease in resistance from said input electrode to the ground electrode. For example, a unit comprising ten neon tube sections operated very satisfactory on a 7,000 volt neon transformer when the resistors had the following values: 5, 1.5, 1, .6, .4, .3, .25 .2, .15 megohm and the distance between electrodes was approximately three feet but may be more; While, except for the first resistor or 'two,the values decline roughly "at the rate of two-thirds the. preceding resistor, a rather wide latitude is permissible. The tubing lengths and therefore the electrode spacing is of course, a factor determining the relative values of the resistors, v

"Beforethe glow discharge column ionizes, its resistance is high, consequently the current flows principally through the resistors; but when the latter case several or all of the intermediate elecv trodes may be the series connected, end electrodes of the different tubing sections.

The neon tubing lis provided throughout its length with a grounded distributed capacitancegrounded without contact with the terminals of the tubing section. The end or groundelectrode I, however, being grounded may be connected with the capacitance 5. i I V 'An electrical path 0 parallel to the glow discolumn once ionizes, its resistance materially drops and the resistors carry only a nominal current. In effect, the resistors form a distributed resistance network which sufficiently supplements the distributed capacitance whereby the attenuated region embraces only one or two sections so that from an ordinary viewing distancethere is a definite line of demarcation between the illuminated and un-illuminated portions of the tubing." The distributed capacity P ovided by the extended external electrodes 5', although of itself incapable of causing an appreciable mobile or progressive glow discharge at commercial frequencies, has the effect of stabilizing the'action of the resistors. That is, without the capacitive electrode, the glow in each section is likely to fail to'ionize at the proper time, but jump or flash on after the potential has raised substantially above threshold value, the tubing section may glow for a half cycle then fall to ionize for several cycles. This materially disturbs the desired even progress in illumination. The capacitive coupling the end of a preceding unit.

afforded by the external electrode I not only causes the glow to be sustained, once the tubing section ionizes, but also, apparently, facilitates ionization at a. point which the glow is barely discernible. The eflect is that of a uniform progression of light giving no hint that the resistors divide the tubing into sections, and the appearance closely approximates the writing or progressive effect heretofore produced only by means offhigh frequencycurrent.

Unlike a high frequency control system, the brilliancy of the tubing, except for its comparatively short attenuated. leading zone, is almost uniform; whereas in a high frequency control system there is a deflnitegradation in brilliancy from one end to the other, even when the tubing becomes completely illuminated. This distinction is important, for it has been found necessary to limit high frequency controlled units to approximately fifteen feet to avoid undue difference in brilliancy between the beginning of one unitand With my system herein disclosed, thirty, forty or even more feet may be incorporated in a single unit. I

By rearrangement of the resistor values from the graduated range suggested hereinbefore a wide variety of mobile effects may be obtained, for example, wherever higher resistors are placed, the corresponding sections will illuminate first. while those controlled by lower resistorswill follow in sequence. Thus, illumination may appear from both ends, from several points throughout the length of the tubing and progress in. two directions or in one direction until completely illuminated. In all cases the distributed capacity has a. stabilizing effect eliminating erratic or jerky sequencing. a

With the arrangement shownin Figure 1, each resistor need only stand its'proportionate share of the total voltage between the extremities of the neon tubing I. Thus, if a ten section tubing is subjected to 10,000volts each resistor need withstand only 1000 volts.

It is not mandatory that the resistors be con-,.

nected in series with each other, but comparable operation may be obtained with the arrangement shown in Fig. 2. Here, the resistors 2| are connected in parallel with each other, each ioining a common lead 22 which may be grounded and connected to the respective leads l of the intermediate electrodes If a high capacity network such as the coating shown in Fig. 4 is provided,

the resistors 2| may be equal in value. Resistors of one megohm value have proven satisfactory, but the resistor value is not crit cal and may vary materially, particularly if various" mobile effects are desired. i

Still further, it is possible to combine the circuits as shown in Fig. 3. In sodoing it is not necessary that each intermediate electrode be its ends to a'source of low frequency current and a contact or brush 5!. A brush 62 is mounted on a shaft 63 driven by a motor Gland engages the winding. The shaft may carry a slipring 85 connected with the brush and upon which rides a contact 65.. In addition a cam "may, be mounted on the shaft to controla switch 68 in series with the brush 62 so as to permit travel of the brush between the ends of the winding. Leads from the switch and the supply to the transformer 6| connect to the transformer l2.

Not only one but several transformers may be connected so thatseveral tubing units maybe ing? the, letter S, the illumination maybe caused to progress faster in the outer or longer tube than in the inner: or shorter tube so that the light front is maintained roughly coincident with radiuslines drawn through the tubes. This desirable result is easily obtained with the resistor circuit shown in Fig. 2 for the reason that the electrodes may be moved closer or spread out a substantial amount without appreciable change in the time required for the light to progress. Thus, assuming a given rate of power increase,

increased spacing causes th light to progress faster, whileldecreased spacing caused the light to progress slower. With the arrangementshown in Figs. 1 and3 the resistor values are theprincipal controlling factor. p

Heretofore, because of the difficulty in controlling the relative progression of illumination in a plurality of tubes, it has'not been practical to cause "writing of a letter or character with more I than one tubeunit. This definitely limitedthe writing or progressiv effect to smaller. signs.

. Whereas, with my arrangements, the large signs sponding transformers II; also, as in Fig. 7 a

main switch 15 isin series with the transformer circuit to open it when the cycle of operation is completed. With this arrangement, several tubing sections each from twenty to fifty feet in length may be written in sequence. By adjustment of therelative positions of the several brushes 12, all indication of a break or pause between the tubing sections may be'eliminated.

Furthermore, as in Fig. '7, 'notonly onebut several sections may bewritten simultaneously. 7

Reference is directed to Fig. 9. Again, a carbon brush transformer 8| is illustrated. Two

windings 82'and 83 are provided each occupying one half the circle and each would reverse to the that the difference in resistor values between sections may be materially less than the values hereinbefore given.

With reference to Fig. 7, a carbon brush transformer BI is shown. This type of transformertis essentially an auto-transformer in which the core is ring-shaped with a torus winding connected at other so thatthe output is graduated from zero to one-hundred percent and back to zero. One or several brushes may ride on the windings and be suitably connected through slip rings to corresponding neon transformers and their tubing sections. With, for example, three brushes 84, a very novel and striking effect is'obtaine d; particularly if the tubing sections differ in color.

Light progresses in the different tubing sections -;in out-of-phase relationship so that one color blends with the others. and the blending of: color progresses from one end to the other. of the tubing sections.

Referenceisnow directed to Fig. inwhich a 'I'hyratron control circuit 9 is shown in the primary circuit of the neon transformer I2; and attention is also directed to Fig. 11 in which the control circuit 9 is shownin the secondary circuit of the transformer; Operation in either location is similar, but advantage is gained by location in the secondary circuit for the reason that the power which a Thyratron of a given rating may handle increases with increased voltage.

Control may be effected by severalconventional manners such as a variable condenser 92, variable resistor 83; or variablev reactance 94.

A'Thyratron is essentially a current control means. That is, the voltage remains constant while the average current output isvaried, preferably from approximately zero to onehundred percent. The neon tubing has a'predetermined critical breakdown voltageQand the voltage input from the Thyratron'control is maintained above this point. t tation in current, the leakage to ground through the resistors tend to lower the voltage in the remainder of the neon tube below this critical voltage, and consequently as the average current supply is increased the critical voltage is reached in the several units of the tubing in sequence, de-

pending upon the arrangement of the resistors, and the illumination is caused to progress.

Because ofthe fact that with the Thyratron alternating current connected to the extreme However, because of thelimicontrol the potential is maintained and current only is regulated, there is'less tendency for the tubing sections toflashor flicker as ionization is initiated than is theficase where the voltage input is varied. Therefore, current or 'I'hyratron these controls have successfully controlled the writing effect in theneon tubing, other controls input or power input the neon tubing may be employed.

fcontroland the capacitive'coupling afforded by current is increased.

electrodes of said tubing and means for varying the power of said source as applied to said electrodes.

2. In a mobile glow discharge system: glow discharge tubing, adapted when energized to support a glow discharge column therein; a resistance network communicating at intervals with said glow discharge column; a distributed capacitance along said tubing; "a source of alternating current connected with said tubing and means for varying the power of said source as applied to saidelectrodes.

3. In a mobile glow discharge system: glow discharge tubing; a source of alternating current connected to the extremities 01' said tubing to effect an ionized glow discharge therein; a controller interposed between said extremities of said tubingand said power source for gradually and uniformly changing the power input thereto; parallel capacity and resistance circuits so dittributed along said tubing to effect a progression of a luminous ionized discharge in said tubing as the power input from said source of alternating 4. An-animated electric sign adapted to operate on a source of low frequency current such as commercial sixty cyclecurrent, comprising: glow discharge tubing having end electrodes and intermediate electrodes; a transformer having a primarycoil connectedwith said source of low frequency current and a high potential limited currentsecondary coil connected to the end electrodes of said tubing; means for progressively varying the effective power; output from said which gradually increase the voltage-or current V In advertising art :towhich the present inven tion'is directed, novelty in appearance is of. primary importance; ,Due to the almost infinite selection of resistor combinations, and wide range of controller rates both uniform and variable,

the number of-progressive or mobile effects obtainable is practically unlimited, thus insuring the requisite novelty. I A

Reference is directed to Figure 6 in which is illustrated a modified formof my invention. In

the arrangement here shown, the neon tubing 5! is provided with a series of electrodes 52, therein connected by resistors 53, all within the tubing.

--Such resistors may be continuous from electrode to electrode orbe relatively short and the remaining distance occupied by a conductor; however such yconductor should be insulated from a the gaseous column within the tubing. Resistor valuesare comparable to those used with the arrangements shown in Figs. 1, 2, and 3;

Although I haveshown and described a particular embodiment of my invention, I do not wish to be limited theretobut desire to include in the scope of my invention the, constructions,

transformer to said tubing; a plurality of resistors connectedto said intermediate electrodes and forming a resistance network by-passing the electrical path through said tubing between said end electrodes; and a metal coating partially covering said tubing and forming therewith an external distributed cathode capacitively coupled with the gas column within the tubing.

5. An animated electric sign adapted to operate on a source'of low frequency current such as commercial sixty cycle current, comprising: glow discharge tubing having end electrodes and intermediate electrodes; a current limiting means interposed between said source of low frequency current and the end electrodes of said tubing; means for progressively varying the effective power output from said current limiting means to said tubing; a plurality of resistors connected to said intermediateelectrodes and forming a resistance network by-passing the electrical path through said tubing between said end electrodes; and a metal coating partially covering said tubing and forming therewith an external distributed cathode capacitively coupled with the gas column within the tubing.

6. An animated electric sign adapted to operate on a source of low frequency current such as commercial sixty cycle current, comprising glow discharge tubing including end electrodes and intermediate electrodes, all of the cold cathode type. one end electrode being grounded; resistors connected to the intermediate electrodes and forming a resistance network to ground; means having a high potential, limited current output interposed between said source of low frequency current and connected directly with said end electrodes and indirectly with said intermediate electrodes through said resistance network; a controller for progressively varying the effective power output from said means whereby, by reason of said resistance network, ionization progresses correspondingly in the sections of tubing between said electrodes; and a metal coating partially covering said tubing and forming therewith an external distributed cathode capacitively coupled with the gas column, said coating being grounded to said grounded electrode.

'1. An animated electric sign adapted to operate on a source of low frequency current, comprising: glow discharge tubing having end electrodes andintermediate electrodes; a resistance network connected to said intermediate electrodes; a high potential source of low frequency current connected with said end electrodes and with said intermediate electrodes through said resistance network; a controller progressively changing the effective power output from said source to said tubing and said resistance network adapted to cause the sections of tubing between said electrodes to ionize in corresponding progression; and means for stabilizing the ionization in each section as the threshold ionization potential is exceeded.

8. An animated sign as specified in claim 7 wherein said stabilizing means is incorporated in said controller and includes a device for maintaining a high potential across said tubing while the current applied to said tubing is varied.

9. An animated sign as specified in claim '7, wherein said stabilizing means comprise a capacitance distributed along said tubing.

10. In a mobile glow discharge system; glow discharge tubing; a resistance network connected at spaced points to said glow discharge tubing; a source of high potential alternating current connected to the extremities of said tubing and to said resistance network whereby, upon progressive change in the effective power output from said source to said tubing, the sections of said tubing between said points ionize in corresponding progression; and means for stabilizing and sustaining ionization in each section as the threshold ionization potential occurs therein.

v 11. A mobile glow discharge system as set forth in claim 10 wherein said stabilizing means includes a controller for progressively varying the current output from said source while maintaining a substantially high potential across the extremities of said tubing.

12. A mobile glow discharge system as set forth in claim 10 whereinsaid stabilizing means includes a controller for progressivew varying the current, output from said source while maintaining a substantially high potential across the extremities of said tubing. and a distributed capacitance along said tubing.

13. A mobile glow discharge system as set forth in claim 10 wherein said stabilizing means includes an external metal coating distributed along said tubing capacitively coupled with the gas column within said tubing.

14. A gaseous glow discharge tube of extended length having: an external cathode extending lengthwise thereof; an anode within one end of said tube exposed to the gas column therein; a series of internal cathodes positioned within said tube at spaced points and likewise exposed to the gas column therein; and an external resistance network connecting said internal cathodes with said external cathode. 15. In a mobile glow discharge system: glow discharge tubing; an anode within one end. of said tubing; a cathode within the other end of said tubing; a series of intermediate cathodes within saidtubing; an external resistance network connecting said intermediate cathodes with said end cathodes; and an external cathode ex: tending along said tubing, said external cathode conductively connected with said end cathode and capacitively associated with the interior of said tubing.

16. A glow discharge means adapted for mobile glow discharge effects comprising: tubing containing a gas adapted, when ionized, to support a glow discharge; end electrodes and spaced intermediate electrodes within said tubing in electrical contact with said gas; an external electrode in electrical contact with one of said electrodes and capacitively coupled with the gas within said I tubing.

17. In a mobile glow discharge system: a series of glow discharge tubes forming separate en- 7 velopes, each including electrodes at least in the extremities thereof having external connecting means adapted to connect said tubes in electrical series; and externalresistors joined to said connecting means and forming a resistance network to ground, one extreme electrode of said series of glow discharge tubes likewise being grounded.v

18. In a mobile glow discharge system: a series of glow discharge tubes forming separate envelopes, each including electrodes at least in the extremities thereof having external connecting means adapted to connect said tubes in electrical series; external resistors joined to said'connecting means and forming a, resistance network to ground, one extreme electrode of said series of glow discharge tubes likewise being grounded; a limited current high potential source connected to the extreme electrodes of said series ofglow discharge tubes; and means for progressively changing the effective power output from said source to said tubes.

19. In a mobile glow discharge system: a series of glow discharge tubes forming separate envelopes, each including electrodes at least in the extremities thereof having external connecting means adapted to connect said tubes in electrical series; and external resistors joined to said connecting means and forming-a resistance network to ground, one extreme electrode of said series of glow discharge tubes likewise being grounded; an external grounded cathode distributed along said tubes and capacitively coupled with the gas columns therein,

20. In a mobile glow discharge system: a series of glow discharge tubes forming separate en-" velopes, each including electrodes at least in the extremities thereof having external connecting means adapted to connect said tubes in elec-.

trical series; and external resistors joined .to said connecting means and forming a resistance network to ground, one extreme electrode. of said series of glow discharge tubes likewise being 

